Mesh is Weirdly Deformed in Object & Sculpt Modes
I have seen results like this after adding new geometry to an object with a multires modifier. It seems having flipped normals contributes to this.

As your learning, I suggest you delete the multires, go into edit mode and select all vertices, CtrlN to re-calculate the normals, add a new multires modifier then re-sculpt.

If you want to keep your sculpt data the only fix I can come up with is to apply the multires, go into edit mode, select the stray vertices and use smooth to bring them back into place. Press W and select smooth or find Smooth Vertex in the spacebar menu, then use ShiftR to keep repeating the last step.

I think I found a way to reliably re-create the issue so will report a bug.